1. Technical Field
The invention relates generally to boring machines and, more particularly, to a drive mechanism for a subterranean boring machine. Specifically, the invention relates to a supplemental drive mechanism that advances and retracts the sled of a subterranean boring machine along a track.
2. Background Information
Subterranean boring machines are used to install subterranean piping without excavating a trough. A subterranean boring machine typically includes a sled that is driven along a track when the machine is configured to install subterranean piping. The sled carries a rotation mechanism that rotates a cutting head in front of the pipe that is being installed. The sled is translated in the forward direction by a translation mechanism that engages the track and drives the sled forward. The pipe includes a rotating auger that draws soil and rock away from the cutting head and discharges the material outside of the subterranean location. The combined effect of the translation mechanism and the rotation mechanism causes the pipe to be driven into its subterranean location. While subterranean boring machines known and understood in the art are effective for their intended purposes, such subterranean boring machines have not, however, been without limitations.
One problem associated with subterranean boring machines is their slow speed of operation. The translation mechanism that drives the sled forward typically includes a pair of dogs that engage drive holes formed in the track and a pair of hydraulic cylinders that expand between the dogs and the sled to drive the sled forward. Inasmuch as the hydraulic cylinders are of limited length, the track is formed with a plurality of regularly spaced drive holes, typically no more that thirty inches apart, into which the dogs must be incrementally engaged. In operation, the dogs engage one set of drive holes and the hydraulic cylinders are expanded driving the sled forward. Once the hydraulic cylinders have expanded to their maximum position, the dogs are released from engagement with the drive holes and the hydraulic cylinders are collapsed until the dogs are aligned with the next consecutive set of drive holes with which the dogs are then engaged. The process must be repeated sequentially with each set of drive holes, resulting in a tedious operation.
Once the sled has been advanced from the initial end to the terminal end of the track and has driven the pipe into the subterranean location by an equal distance, the pipe is released from the sled, and the sled is retracted from the terminal position back to the initial position. Sections of pipe and auger are then added to the ends of the pipe and auger sections that protrude from the subterranean location. The driving process is then repeated. In one example, the track may be thirty-two feet long with the pipe and auger sections being the same length. The incremental driving process is repeated until enough sections of pipe have been driven into the subterranean location to achieve the desired overall length of the pipe.
To move the sled in the reverse direction, the same hydraulic cylinders that drive the sled forward must again be repeatedly expanded and collapsed in conjunction with incremental engagement and disengagement of the dogs in the drive holes. That is, the dogs are retracted from a pair of drive holes and the hydraulic cylinders are expanded to drive the dogs in the rearward direction until aligned with the previous set of drive holes. The dogs are then engaged with the drive holes and the hydraulic cylinders collapsed to retract the sled in the rearward direction. The retraction process is repeated until the sled reaches the initial position. The retraction process consumes as much time as the driving process even though no pipe is being driven and the sled is unloaded.
A need thus exists for a drive mechanism that can quickly retract and advance an unloaded sled of a subterranean boring machine without the need to incrementally engage the dogs of the translation system in sequentially positioned drive holes.
In view of the foregoing, an objective of the present invention is to provide a drive mechanism for quickly retracting and advancing the sled of a subterranean boring machine along a track.
Another objective of the present invention is to provide a drive mechanism that increases the installation speed of subterranean piping.
Another objective of the present invention is to provide a drive mechanism that can be retrofitted to existing sleds of subterranean boring machines.
Another objective of the present invention is to provide a drive mechanism that serves as an adjunct to the translation system of a subterranean boring machine that is used to drive a pipe into a subterranean location.
Another objective of the present invention is to provide a drive mechanism that selectively advances and retracts a sled of a subterranean boring machine more quickly than the translation mechanism can advance and retract the sled.
Another objective of the present invention is to provide an adjunct drive mechanism that can advance and retract the sled of a subterranean boring machine for purposes other than driving a pipe into a subterranean location.
These and other objectives and advantages are obtained by the improved drive mechanism of the present invention that is adapted to translate a sled of a subterranean boring machine along a track, the general nature of which can be stated as including at least a first drive wheel, the at least first drive wheel adapted to rollably engage the track, and a drive motor operatively connected with the at least first drive wheel.
Other objectives and advantages are obtained from the method of the present invention for excavationless installation a subterranean pipe below a grade, the general nature of which can be stated as including the steps of attaching the pipe to a sled of a subterranean boring machine, thrusting the sled along a track with a translation mechanism, and retracting the sled with a drive mechanism.
Still other objectives and advantages are obtained from the combination of the present invention of a sled of a subterranean boring machine and a drive mechanism, the sled adapted to be translated and retracted along a track, the track being formed with a plurality of drive holes, the general nature of which can be stated as including a sled and a drive mechanism mounted on the sled, the drive mechanism having at least a first drive wheel and a drive motor, the at least first drive wheel operatively connected with the drive motor, the drive mechanism adapted to retract the sled along the track free of interaction with the drive holes.